Check a Path Exists in a Model

It checks whether a path, usually an indirect path, exists in a model.

Usage

check_path(x, y, m = NULL, fit = NULL, est = NULL)

Arguments

x

Character. The name of predictor at the start of the path.

y

Character. The name of the outcome variable at the end of the path.

m

A vector of the variable names of the mediators. The path goes from the first mediator successively to the last mediator. If NULL, the default, the path goes from x to y.

fit

The fit object. Currently only supports a lavaan::lavaan-class object or a list of outputs of lm(). It can also be a lavaan.mi object returned by lavaan.mi::lavaan.mi() or its wrapper, such as lavaan.mi::sem.mi(). If it is a single model fitted by lm(), it will be automatically converted to a list by lm2list().

est

The output of lavaan::parameterEstimates(). If NULL, the default, it will be generated from fit. If supplied, fit will ge ignored.

Value

A logical vector of length one. TRUE if the path is valid, FALSE if the path is invalid.

Details

It checks whether the path defined by a predictor (x), an outcome (y), and optionally a sequence of mediators (m), exists in a model. It can check models in a lavaan::lavaan-class object or a list of outputs of lm(). It also support lavaan.mi objects returned by lavaan.mi::lavaan.mi() or its wrapper, such as lavaan.mi::sem.mi().

For example, in the following model in lavaan syntax

m1 ~ x
m2 ~ m1
m3 ~ x
y ~ m2 + m3

This path is valid: x = "x", y = "y", m = c("m1", "m2")

This path is invalid: x = "x", y = "y", m = c("m2")

This path is also invalid: x = "x", y = "y", m = c("m1", "m2")

Examples

library(lavaan)
data(data_serial_parallel)
dat <- data_serial_parallel
mod <-
"
m11 ~ x + c1 + c2
m12 ~ m11 + x + c1 + c2
m2 ~ x + c1 + c2
y ~ m12 + m2 + m11 + x + c1 + c2
"
fit <- sem(mod, dat,
           meanstructure = TRUE, fixed.x = FALSE)

# The following paths are valid
check_path(x = "x", y = "y", m = c("m11", "m12"), fit = fit)
#> [1] TRUE
check_path(x = "x", y = "y", m = "m2", fit = fit)
#> [1] TRUE
# The following paths are invalid
check_path(x = "x", y = "y", m = c("m11", "m2"), fit = fit)
#> [1] FALSE
check_path(x = "x", y = "y", m = c("m12", "m11"), fit = fit)
#> [1] FALSE